During storage, chewing gum has a tendency to lose or gain moisture from the surrounding atmosphere depending on the surrounding temperature, relative humidity, and packaging, and also depending on the shape and formulation of the chewing gum. Sugar-containing chewing gums, for instance, typically contain corn syrup and a small amount of humectant such as aqueous sorbitol or glycerin. Such sugar-containing chewing gums have a tendency to dry out and become brittle when stored under relatively dry conditions of 50% relative humidity and lower. The tendency of sugar gums to dry out and become brittle is particularly apparent at higher ambient temperatures.
Sugarless chewing gums are typically designed to contain lower amounts of moisture than sugar-containing gums. In sugarless gums which are sweetened with aspartame or other moisture-susceptible artificial sweeteners, it is important to maintain a low moisture content in order to prevent loss of sweetness and flavor qualities. However, due to their low initial moisture content, these sugarless gums tend to gain moisture at above 40% relative humidity, causing wetness of the chewing gum and degradation of the aspartame or other moisture-susceptible artificial ingredients.
Various technologies have been developed for the purpose of protecting chewing gum from moisture loss, moisture gain and other adverse changes which result from storage. For example, packaging techniques have been developed which provide sealed, high quality protective packaging for individual chewing gum sticks. One such technique is disclosed in U.S. Pat. No. 5,048,260 to Raymond et al.
Other techniques of protecting chewing gum from adverse environmental conditions have involved modifying the chewing gum formulae so as to encapsulate or otherwise protect the individual chewing gum ingredients which are environmentally susceptible. U.S. Pat. No. 4,822,622 to Dokuzovic et al. discloses the use of a protective barrier film through the center of a chewing gum to separate a flavor-containing chewing gum layer from an aspartame-containing chewing gum layer. The barrier film components which are disclosed include gelatin, acacia gum, agar, algin and derivatives, carrageenan and salts thereof, arabinogalactan, baker yeast, glycan, carboxymethylcellulose, carob bean gum, cellulose gum, furcellaran and salts thereof, guar gum, gum arabic, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, Irish moss gelose, karaya gum, locust bean gum, methylcellulose, methylethyl cellulose, pectin, propylene glycol alginate, propylene glycol ether of methylcellulose, sodium carboxy methylcellulose, tragacanth gum, xanthan gum, shellac, and mixtures thereof.
U.S. Pat. No. 4,568,560 discloses a method for encapsulating active ingredients in a coating composition comprising a water soluble film forming composition, an enteric compound and a plasticizer for the film forming composition. U.S. Pat. No. 4,824,680 to Bernatz et al. discloses a method of producing a sugar-based chewing gum having improved wrappability.
Still other techniques of protecting chewing gum from adverse environmental conditions have involved coating the chewing gum with an edible film. Most of these techniques have focused on the film coating of chewing gum tablets and other confectionery tablets, as opposed to chewing gum sticks. U.S. Pat. No. 4,802,924 and PCT Publication WO 87/07902 disclose the coating of pharmaceutical tablets, foods, confectionery forms and the like with polydextrose, or a combination of polydextrose and cellulosic polymer, or a layer of polydextrose overcoated by a layer of cellulosic polymer. German Patent No. DE 3,043,914 discloses the coating of pharmaceuticals, confectionery products and foods, with an edible film containing methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, cellulose acetate phthalate, ethyl cellulose, polyvinyl pyrrolidone, sodium ethyl cellulose sulfate, corn protein (zein), and/or poly (vinyl acetate phthalate).
U.S. Pat. No. 4,810,534 to Seaborne et al. discloses a method for preparing a low water permeable, edible film containing cross-linked shellac and one or more edible sources of polyphenolics, benzaldahyde and derivatives, acetylated monoglycerides, polyglycerol esters, straight chain monocarboxylic acid and dicarboxylic acids. U.S. Pat. No. 4,777,046 to Iwakura et al. discloses a sheet-like preparation comprising a drug, a gelatin or agar, gluten, a carboxyvinyl polymer, a polyhydric alcohol, a gum, a wax and a sheet-like support. PCT Publictions WO 87/03453 and WO 86/00501 both disclose methods of preparing preformed edible films which include a layer of a hydrophilic polymer selected from the group consisting of edible, film-forming carbohydrates and proteins, and a lipid layer adhered to the hydrophilic layer.
There is a need or desire in the chewing gum industry for a coating and coating method which is uniquely suited to the prevention of moisture absorption and moisture loss from stick chewing gum. Chewing gum sticks, due to their high ratios of surface area to volume, are susceptible to rapid changes in their moisture content when exposed to adverse environmental conditions. Also, stick gums are more difficult to uniformly coat then pellet gums due to their large surface areas.